1. Field of the Invention
This invention relates to a structure of seal materials to seal liquid crystal material injected between a facing electrode substrate carrying a facing electrode and a drive circuit substrate carrying a drive circuit of a liquid crystal display apparatus, and further relates to a method for fabricating a liquid crystal display apparatus having such structure of the seal materials.
2. Description of the Related Art
In a liquid crystal display apparatus, a drive circuit substrate carrying TFT (Thin Film Transistor) devices for driving liquid crystal material and a facing electrode substrate carrying a facing electrode to be faced to each of the TFT devices are piled together with a spacer and seal materials. The liquid crystal material is then injected in a space between the above mentioned drive circuit substrate and facing electrode substrate through an injection gate provided at one portion of the seal materials.
FIG. 3A is a plan view for showing a seal structure employed in a conventional liquid crystal display apparatus and FIG. 3B is a sectional view taken along a line IIIBxe2x80x94IIIB of the conventional liquid crystal display apparatus depicted in FIG. 3A.
In a following discussion, a direction of an arrow xcex1 is called an upper side, an opposite direction thereof is called a lower side, a direction of an arrow xcex2 is called a left side and an opposite side thereof is called a right side.
As shown in FIG. 3A, a rectangular effective picture element area 12 is positioned at a central part of a rectangular facing electrode substrate 10 and a plurality of facing electrodes and an orientation film are provided (not shown in the figure) on this facing electrode substrate 10 within this effective picture element area 12. Seal materials 14 are arranged at peripheries of this effective picture element area 12. These seal materials 14 are formed in a rectangular shape along peripheries of the effective picture element area 12 like a rectangular picture frame.
These seal materials 14 are formed almost all peripheries of the effective picture element area 12 except a portion of an injection gate 16 for injecting the liquid crystal material. In addition, the injection gate 16 is to be sealed from outside by a sealant 20 after injection of the liquid crystal material into a space between the facing electrode substrate 10 and a drive circuit substrate 1.
In addition, an electrode portion 18 to connect this liquid crystal display apparatus to an outside circuit by a connector (not shown in the figure) is provided on the upper side of the drive circuit substrate 1.
Then the facing electrode substrate 10 is piled on the drive circuit substrate 1 with afore-mentioned predetermined space by way of the above mentioned seal materials 14 and a plurality of spacers supported by the seal materials 14, in which each of the spacers may be a small ball. Both the facing electrode substrate 10 and the drive circuit substrate 1 are joined together by hardening of the seal materials 14.
By the way, spaces between the effective picture element area 12 and the seal materials 14 surrounding peripheries of the effective picture element area 12 is not uniform in the conventional liquid crystal display apparatus.
In other words, in FIG. 3A, a space between an upper side periphery of the effective picture element area 12 and an upper side of the seal materials 14 is defined as Axe2x80x2 and a space between a left or right side periphery of the effective picture element area 12 and a left or right side of the seal materials 14 is defined as Bxe2x80x2. In this case, the space Axe2x80x2 and the space Bxe2x80x2 are not equal and in FIG. 3A, the space Axe2x80x2 is larger than the space Bxe2x80x2 (Axe2x80x2 greater than Bxe2x80x2). This is because wiring for the above described electrode portion 18 and a peripheral circuit portion for driving TFT devices are concentrated near the upper side of the drive circuit substrate 1. These TFT devices are mounted on the drive circuit substrate 1.
However, when the space between the effective picture element area 12 and the seal materials 14 shows non-uniform, uniformity of the space between the facing electrode substrate 10 and the drive circuit substrate 1 in the effective picture element area 12 is deteriorated in case of jointing both facing electrode substrate 10 and the drive circuit substrate 1.
In addition, in the conventional seal materials of the liquid crystal display apparatus, a portion of the seal materials are removed at the injection gate 16 for injecting liquid crystal material and this removed portion also causes the non-uniformity of the space between the facing electrode substrate 10 and the drive circuit substrate 1 in the effective picture element area 12.
Quality of the liquid crystal display apparatus is deteriorated by this non-uniformity of the space between the facing electrode substrate 10 and the drive circuit substrate 1 in the effective picture element area 12.
FIG. 4 is an illustration showing the condition where an interference fringe is observed by irradiation of a sodium vapor lamp to the conventional liquid crystal display apparatus that has non-uniform space between the facing electrode substrate 10 and the drive circuit substrate 1.
As shown in FIG. 4, an interference fringe 24 is observed with curved form along peripheries of the effective picture element area 12. And further the interference fringe 24 is invaded even into the effective picture element area 12, so that it is understood that the space between the facing electrode substrate 10 and the drive circuit substrate 1 is not uniform.
In order to correct the non-uniformity of the space between the facing electrode substrate 10 and the drive circuit substrate 1, the space between the outer periphery of the effective picture element area 12 and the inner periphery of the seal materials 14 is set to be uniform by enlarging partially the width of the seal materials 14. But in this case, it is probable to occur a disorder of the orientation between the seal materials and the liquid crystal material, so that there is a problem that the facing electrode substrate 10 and the drive circuit substrate 1 have to be put on one another with increased pressure.
In addition, another spacer is may be provided in the effective picture element area 12 at the facing electrode substrate 10 and the drive circuit substrate 1, but in the case where the additional spacer is formed by a TFT fabrication processing at boundaries of the picture element of the drive circuit substrate 1, it becomes more difficult to correct the non-uniformity of the space between the facing electrode substrate 10 and the drive circuit substrate 1 because of the strength of the liquid crystal display apparatus.
A primary object of the present invention is to present a liquid crystal display apparatus having a new structure of seal materials which can improve an uniformity of a space between a drive circuit substrate and a facing electrode substrate in an effective picture element area and a method for fabricating such liquid crystal display apparatus.
In order to achieve the above object, a liquid crystal display apparatus of a type having a drive substrate and a facing electrode substrate superimposed and joined each other via spacer and seal material is disclosed. The drive substrate carries drive devices for driving liquid crystal material, the facing electrode substrate carries facing electrodes facing to the drive devices, and the liquid crystal material is injected between the drive substrate and the facing electrode substrate, wherein the seal material includes an outer seal formed along outer peripheries of the drive substrate and the facing electrode substrate and an inner seal formed inside of the outer seal, and a space between the out side portion of an effective picture element area constituting drive devices and an inside portion of the outer seal facing to the effective picture element area or an inside portion of the inner seal can be formed in approximately uniform.
In the liquid crystal display apparatus of this invention, the seal materials seal a space between the drive circuit substrate and the facing electrode substrate when the drive circuit substrate and the drive circuit substrate are superimposed and joined each other.
The seal materials include an outer seal and an inner seal, and the outer seal is formed along outer peripheries of the drive circuit substrate and the facing electrode substrate. In addition, the inner seal is partially arranged at inside of this outer seal.
In such seals as described, the space between the outside portion of an effective picture element area having drive devices and an inside portion of the outer seal facing to the effective picture element area or an inside portion of an inner seal can be formed in approximately uniform.
Accordingly it becomes possible to superimpose the drive circuit substrate and the facing electrode substrate each other smartly by using seal materials having pattern as described above, and particularly the drive circuit substrate and the facing electrode substrate are joined with proper pressure at the effective picture element area, so that the space between two substrates can be kept uniform at the effective picture element area of the liquid crystal display apparatus. Resultantly, the quality of the liquid crystal display apparatus can be improved by improving the uniformity of the space between the drive circuit substrate and the facing electrode substrate at the effective picture element area.